I started working at a bakery recently and on the first day I was amazed to see a large plastic garbage pail full of very sour levain. Before the day was out, we dumped the whole thing (about 35lbs.) into the mixer and turned out sourdough loaves. This large volume of very ripe levain originated from 1/2 lb. of flour only a day before.
The shop I work for calls the original small-scale culture "mother" while I'm sure other people call it other things, like chef or barm. This is fed daily with 1/2 lb. bread flour 1/2 lb. water.
From the mother (before feeding) we pour off whatever will easily pour out without shaking or scraping, and leave the residue to feed as above. The pour off is fed again, this time 2 lbs flour 2 lbs water, and at this point they call it starter. The volume has quadrupled.
Twelve hours later, the starter is fed as a whole culture, aiming for whatever volume of levain will be needed for a day's baking. Usually this is in the 30 lb. range, an increase of about eight times over the starter. So the feeding is half flour half water by weight to reach the needed levain. This whole process is repeated daily. The resulting levain smells very sour, but is quite liquid.
The terms "mother" "starter" and "levain" seem to be quite arbitrary, since the composition of each is identical, differing only by volume.
I had always wondered about how much you could multiply your starter and how quickly. Now I know.